1. Field of the Invention
This invention relates to a sewing apparatus including a cassette mount to which a thread cassette is detachably attached and a threading mechanism automatically passing a thread through a needle hole, and a needle bar position control program for such a sewing apparatus.
2. Description of the Invention
Sewing apparatus have conventionally been provided including a cassette mount to which a thread cassette is detachably attached. The thread cassette accommodates a thread spool on which a thread is wound. The thread drawn from the thread cassette serves as a needle thread. The thread drawn from the thread cassette attached to the cassette mount is caused to extend between a pair of thread tension discs and then caught by a needle thread take-up lever. The thread is further caused to pass through a hole of a sewing needle mounted to a needle bar, thereby being set. The assignee of the present application filed a Japanese patent application to which application No. 2002-91558 has been assigned. This Japanese patent application discloses a sewing apparatus including a thread feeding mechanism operated in synchronization with attachment of the thread cassette to the cassette mount, and a threading mechanism. The thread drawn from the thread cassette is automatically passed through the needle hole by the thread feeding mechanism and threading mechanism.
In the foregoing sewing apparatus, the thread feeding mechanism includes a thread catching member and a moving mechanism for moving the thread catching member. Upon actuation of the thread feeding mechanism, the thread catching member is lowered so that the thread drawn from the thread cassette is caught by the thread catching member. The thread is carried near the needle hole and then tensioned in front of the needle hole. The threading mechanism comprises a threading shaft provided along the needle bar so as to be moved up and down and further rotated and a threading hook mounted on a lower end of the threading shaft so as to be allowed to pass through the needle hole. Upon actuation of the threading mechanism, the threading shaft is lowered to be Positioned relative to the needle bar and then stopped. Successively, the threading shaft is rotated so that the threading hook is passed through the needle hole. The thread drawn from the thread cassette has been carried near the needle hole by the thread catching member. The thread is caught by the threading hook having been passed through the needle hole and subsequently, the threading shaft is rotated in the reverse direction so as to be pulled out of the needle hole.
In the sewing apparatus of the above-described type, the needle bar is rocked right and left relative to an arm portion of the sewing apparatus by a needle bar rocking mechanism, so that zigzag stitches and the like are realized. In this case, the needle bar and the threading mechanism are supported on a needle bar frame pivotally mounted on a frame of the arm, so that the needle bar is stopped at any zigzag position when the sewing machine is stopped. On the other hand, the aforesaid thread feeding mechanism is mounted on the frame of the arm, and the thread drawn from the thread cassette is carried to a fixed position relative to the arm.
Accordingly, when the thread cassette has been attached to the cassette mount, a difference is sometimes caused between a position of the thread carried by the thread feeding mechanism and a position of the needle hole, depending upon a zigzag position of the needle bar. Consequently, the threading cannot be carried out sufficiently since the thread carried by the thread feeding mechanism is not caught by the threading hook of the threading mechanism. In this regard, the user may manually locate the needle bar at a predetermined zigzag position when the thread cassette is attached to the cassette mount. However, the user is forced into troublesome operation.
Therefore, an object of the present invention is to provide a sewing apparatus in which the thread drawn from the thread cassette attached to the cassette mount can be passed through the needle hole by the threading mechanism easily and reliably and a needle bar position control program which can be applied to the sewing apparatus.
The present invention provides a sewing apparatus comprising a needle bar, a needle bar rocking mechanism for rocking the needle bar, a thread cassette having a thread accommodating section for accommodating a thread, a cassette mount to which the thread cassette is detachably attached, a threading mechanism for passing the thread drawn from the thread cassette through a hole of a sewing needle mounted on the needle bard a detector for detecting the thread cassette ejected from the cassette mount, and a needle bar position control unit controlling the needle bar rocking mechanism so that the needle bar is rocked so as to occupy a predetermined zigzag position, when the detector has detected the thread cassette ejected from the cassette mount.
In the above-described construction, the needle bar rocking mechanism is controlled by the needle bar position control unit on the basis of detection by the detector when the thread cassette has been ejected from the cassette mount, so that the needle bar is rocked into the predetermined zigzag position where the thread can be passed through the needle eye by the threading mechanism. Thus, when a cassette is to be attached to the cassette mount at a next occasion, the needle bar is located at the predetermined zigzag position where the thread can be passed through the needle eye by the threading mechanism. Accordingly, when the thread cassette has been ejected from the cassette mount, an operation for subsequent attachment of the thread cassette can be automatically carried out without the user being forced into troublesome operation. Consequently, the thread drawn from the thread cassette attached to the cassette mount can be passed through the needle eye by the threading mechanism easily and reliably.
As the aforesaid detector, limit switches or the like may be provided so as to be turned on and off in response to attachment and detachment of the thread cassette to and from the cassette mount, whereupon ejection of the thread cassette is detected directly by the limit switch. Furthermore, when an operating member is provided so as to be operated when the thread cassette is ejected from the cassette mount, operation of the operating member may be detected by a switch or the like, whereby ejection of the thread cassette may be detected indirectly.
The foregoing sewing apparatus may further comprise a thread feeding mechanism catching the thread drawn from the thread cassette and carrying the thread near the needle hole when the thread cassette has been attached to the cassette mount. The thread carried by the thread feeding mechanism may be passed through the needle hole by the threading mechanism. In this case, the predetermined zigzag position of the needle bar can be set so as to correspond to the location of the thread feeding mechanism.
In the above-described construction, the thread carried near the needle hole of the sewing needle by the thread feeding mechanism is passed through the needle hole. Since the predetermined zigzag position of the needle bar can be set so as to correspond to the location of the thread feeding mechanism, the needle bar (needle), a suitable constant positional relationship can usually be maintained Consequently, the threading operation can reliably be carried out.
U.S. patent application No. Ser. 10/392,186 discloses the structure of the threading mechanism of the above-noted type in detail.
The sewing apparatus may further comprise a needle bar up-down movement mechanism moving the needle bar up and down and a needle bar up-down movement stopping unit stopping the needle bar up-down movement mechanism when ejection of the thread cassette from the cassette mount is detected during operation of the needle bar up-down movement mechanism.
In the above-described construction, the up-down movement of the needle bar is stopped by the needle bar up-down movement stopping unit when the thread cassette has been ejected from the cassette mount during operation of the needle bar up-down movement mechanism. Consequently, any trouble due to continuous up-down movement of the needle bar even after ejection of the thread cassette can be prevented. Furthermore, the needle bar can be re-rocked to the predetermined zigzag position for the subsequent attachment of the thread cassette after the needle bar has been stopped.
The sewing apparatus may further comprise a thread tensioning unit adjusting a tension of the thread drawn from the thread cassette attached to the cassette mount and a thread tension control unit controlling the thread tensioning unit so that the thread tensioning unit is opened when ejection of the thread cassette from the cassette mount is detected by the detector during operation of the needle bar up-down movement mechanism.
In the above-described construction, the thread drawn from the thread cassette is reliably released from the thread tensioning unit by the thread tension control unit when the thread cassette is ejected from the cassette mount. Consequently, the thread cassette can be ejected from the cassette mount smoothly without the thread being caught by the thread tensioning unit.
The detector may further detect the thread cassette having been attached to the cassette mount, and the needle bar position control unit may control the needle bar rocking mechanism so that the needle bar is rocked so as to occupy a sewing start Position; a predetermined period of time after attachment of the thread cassette to the cassette mount is detected by the detector.
In the above-described construction, when the thread cassette has been attached to the cassette mount, the needle bar rocking mechanism is controlled by the needle bar position control unit the predetermined period of time after the attachment so that the needle bar is rocked from a predetermined needle rock position to a sewing start position. Consequently, the sewing operation can be started quickly.
In this case, the aforesaid predetermined period of time is desirable to be as short as possible although it needs to be sufficiently long enough to carry out the threading operation by the threading mechanist. According to the study by the inventors, the predetermined period of time is 30 msec.
Furthermore, both the needle bar rocking mechanism and the thread tensioning unit are preferably driven by a single pulse motor. Consequently, the construction of the sewing apparatus can be simplified as compared with the case where two drive sources are provided for the needle bar rocking mechanism and the thread tensioning unit respectively.
The aforesaid needle bar up-down movement mechanism is driven by the spindle further driven by the sewing machine motor. Where an angle of the spindle is 0 (or 360 degrees) when the needle bar (sewing needle) is at an uppermost position, the needle bar is located at a position of height corresponding to a rotation angle of the spindle. The sewing apparatus provided with the aforesaid needle bar up-down movement stopping unit may further comprise a spindle driving the needle bar up-down movement mechanism and a spindle rotation angle detector detecting a rotation angle of the spindle. The needle bar up-down movement stopping unit may stop the needle bar up-down movement mechanism within a Predetermined range of rotation angle so that the needle thread is stopped at a vertical position where the thread can be passed through the needle hole by the threading mechanism, based on a result of detection by the spindle rotation angle detecting unit.
In the above-described construction, when the up-down movement of the needle bar is stopped by the needle bar up-down movement stopping unit, the needle bar is stopped at the vertical position where the thread can be passed through the needle hole by the threading mechanism. Accordingly, when the thread cassette is subsequently attached to the cassette mount, the needle bar is located at the position where the thread can be passed through the needle hole by the threading mechanism. Consequently, the thread drawn from the thread cassette attached to the cassette mount can be passed through the needle hole by the threading mechanism easily and reliably. In this regard, the research by the inventors reveals that the predetermined range of rotation angle is preferably from 20 to 50 degrees.
The invention further provides a needle bar position control program for controlling a position of a needle bar in a sewing apparatus including a needle bar, a needle bar rocking mechanism for rocking the needle bar, a thread cassette having a thread accommodating section for accommodating a thread, a cassette mount to which the thread cassette is detachably attached, a threading mechanism for passing the thread drawn from the thread cassette through a hole of a sewing needle mounted on the needle bar, and a detector for detecting the thread cassette ejected from the cassette mount, the program accomplishing a function of controlling the needle bar rocking mechanism so that the needle bar is rocked so as to occupy a predetermined zigzag position, when the detector has detected the thread cassette ejected from the cassette mount.
The needle bar position control program is applied to a computer provided in the sewing apparatus. In the sewing apparatus, the needle bar rocking mechanism is controlled on the basis of the results of detection by the detector when the thread cassette has been detached from the cassette mount, whereupon the needle bar is rocked to a predetermined zigzag position where the thread can be passed through the needle hole by the threading mechanism. The needle bar position control program may be supplied to users via communication means such as the internet or the like, or may be recorded on a recording medium such as CD, MD or FD to be supplied to the user with the recording medium.